The present invention relates to vinylidene chloride copolymer latexes and improved self-extinguishing or flame-retardant adhesive compositions thereof and, more specifically, to such compositions containing a copolymer latex which is produced from an aliphatic conjugated diolefin, a monoolefinic monomer selected from the group consisting of aromatic vinyl monomers, acrylate esters and methacrylate esters, an ethylenically unsaturated carboxylic acid, and vinylidene chloride.
In recent years, with increasingly higher demand for incombustible interiors in public facilities, extensive attempts or studies (mainly in terms of components to be blended) have been made directed to providing adhesives with a flame-retardant or incombustible property, not only in those adhesives applied to a wide variety of textile products including cushioning materials for railroad cars and automobiles as well as floor and wall materials such as carpets, moquettes, curtains, cushioned floors, etc., but also in those used for various kinds of materials such as in the manufacture of plywood and in the formulation of paints.
Conventionally, flame-retardant blended adhesive compositions for the aforementioned types of materials generally comprise a natural rubber latex, synthetic rubber latex such as styrene-butadiene copolymer, or vinyl acetate or acrylic synthetic resin emulsions, blended with organic or inorganic flame retardants such as halogenated paraffins, halogenated aromatic compounds, phosphorus compounds, alumunium hydroxide, antimony trioxide and so forth. However, in order to obtain satisfactory durable flame retardance in such conventional adhesive compositions, relatively large quantities of relatively expensive flame retardants must be blended in combination. Accordingly, the powder dispersion and blending process (as well as the resulting adhesives) are rendered very expensive and very complicated. Moreover, the prior art flame-retardant adhesive compositions have additional disadvantages in that the blending of such flame-retardants results in decreased latex stability, impedes reactions such as vulcanization and, especially, results in a remarkable reduction in adhesiveness and water resistance which are properties of great importance from a practical point of view.
The use of self-extinguishing halogen-containing latexes such as vinylidene chloride latexes, chloroprene latexes, vinyl chloride latexes, etc., as adhesive components of flame-retardant blended compositions is also well known in the art. In fact, vinylidene chloride latexes having a high chlorine content are known to be extremely useful as adhesive components of flame-retardant compositions because of their remarkably high flame retardance. However, such high chlorine content latexes have the following disadvantages: (1) low colloidal stability or storage stability as well as low stability against metal ions and alkalis; (2) gradual dehydrochlorination occurring when exposed to heat or light, resulting in coloration and deterioration in strength; and (3) limited applicability to many materials by virtue of inadequate adhesiveness thereto. Thus, in spite of the feature of excellent flame-retardance, such high chlorine content vinylidene chloride latexes, as used as adhesive components of flame-retardant blended compositions for various substrates, are extremely limited in their applicable scope. Further, the use of adhesive compositions containing a copolymer latex of vinylidene chloride and butadiene and styrene (U.S. Pat. No. 2,476,967), a copolymer latex of vinylidene chloride-styrene-butadiene-ethylenically unsaturated carboxylic acid (West German Provisional Pat. Publication No. 2,451,627), or a blended latex of vinylidene chloride latex and styrene/butadiene latex is also accompanied by several disadvantages similar to those described above, particularly, inferiority in colloidal stability and instability against heat and light.
In view of the foregoing deficiencies of the prior art flame-retardant adhesive compositions, it is highly desirable to provide self-extinguishing or flame-retardant adhesive compositions which have an improved combination of properties and, especially, which reduce the aforementioned shortcomings of such prior art adhesives.